Eric Cantor unleashed a harsh attack on Obama's national security policies in a speech sponsored by the right-wing Heritage Foundation today, and I've got some video of what may be the best moment: The crowd grumbling audibly in anger when Cantor rebuffed a questioner who suggested Obama is a "domestic enemy."

The key moment comes just before the one-minute mark:

The audience member claimed Obama had put us at greater risk, and asked Cantor: "What would he have to do differently to be defined as a domestic enemy?" That prompted loud, approving laughter from the crowd.

Cantor replied, in part: "No one thinks that the president is a domestic enemy," prompting audible grumbling from the crowd which you can hear on the video at around the 1:10 mark.

A source who was there tells me the grumbling was even more pronounced than the C-Span footage suggests. Indeed, Cantor was forced to repeat the beginning of his next sentence twice in order to get his speech back on track.

Cantor eventually turned the audience to applause by vowing that Republicans would take the country back from Obama.

To be sure, you'll always find a few malcontents in any crowd. But it's worth keeping in mind that this isn't some Tea Party rally. It looked to be made up of donors and more policy-oriented folks. Yet the claim that Obama is a "domestic enemy" was well received, and Cantor's dismissal of it provoked audible groans from at least a few of the attendees.